We’ve all had them via e-mail, but now hoax letters are dropping through local letter boxes promising to deposit large amounts of money in your bank account.

Hertfordshire police have begun a campaign to urge people not to respond to a scam that could leave them in debt and associated with criminal activity.

The letters claim to be from senior government officials in South Africa, or officials within the South African Reserve Bank.

They urge the recipient to open a bank account in their own name so the ‘officials’ can deposit large sums of money generated from over-inflated government contracts.

The fraudsters say that anyone helping them move the funds out of South Africa will be granted 10 to 30 per cent of the cash.

Police say that once the recipient has opened an account in their own name, and sent the details on, the fraudsters can use that account for criminal ends, possibly leaving the account holder liable.

Officers have issued the warning throughout Hertfordshire. They say people who receive such letters should put them in the bin. They should certainly not respond. Once those operating the scam know your details they can use your identity for other fraudulent schemes.

"Hoax letters can come in other forms such as emails or faxes. Please ensure you check thoroughly that any request for personal or bank details is absolutely bona fide," a police spokesman said.